Models hold Samsung phones coated with protective gas for water resilience in this photograph.

South Koreans can now sign up to protect their Samsung Electronics Co.Galaxy S4 phones from sudden dunks into water.

South Korea’s SK Telecom Co., in partnership with a local startup, is testing technology to make smartphones waterproof, and the Galaxy S4 will be its first candidate. The country’s largest mobile carrier said it will provide free coating services to 30,000 users of the smartphone.

The smartphones will be sprayed with a type of carbon gas that will coat the device with a thin, invisible barrier, blocking infiltration of water into the device, Irene Kim, a spokeswoman for SK Telecom said by phone.

It may be a challenge, however, for SK Telecom to prove to its customers that the splash-proof coating service is more than just a marketing gimmick. Samsung has already released waterproof versions of its mobile phones, one of the latest being the Galaxy S4 Active, which the company says can stay submerged for up to 30 minutes in one-meter deep bodies of water.